New Outlook Email Signatures: IT Admin Guide for 2027

Microsoft will start moving Microsoft 365 Enterprise users from classic Outlook to new Outlook for Windows in March 2027. If your company puts email signatures in place with a logon script, a Group Policy file drop or a COM add-in, that setup will not follow your users across. New Outlook keeps signatures in the cloud instead of reading the local Signatures folder, and it does not run COM add-ins at all.

This guide is for the IT admin who owns signatures at a company of 50 to 500 people. It covers the dates, the four things that break, a checklist for the months before March, and the setup that keeps working in both versions of Outlook.

Everything here was checked on 4 November 2026. Microsoft has moved these dates before, so check Message Center post MC949965 in your Microsoft 365 admin center for the latest version.

The dates that matter

Date	What happens
December 2024	Microsoft announces that Enterprise users will be moved from classic Outlook to new Outlook for Windows, with an option to switch back.
20 February 2026	Microsoft updates MC949965 and moves the start of the opt-out phase from April 2026 to March 2027.
1 October 2026	Exchange Online starts blocking Exchange Web Services (EWS) in tenants that did not set up an allow list.
March 2027	Opt-out phase begins. Users are switched to new Outlook and get onboarding prompts. They can still switch back to classic Outlook.
1 April 2027	Microsoft's planned date for the complete shutdown of EWS in Exchange Online.
Later, with 12 months' notice	Cutover phase. Once it is complete, users can no longer switch back to classic Outlook.
At least 2029	Microsoft says existing classic Outlook installations stay supported until at least 2029.

Two notes on the table. Microsoft 365 Business Standard and Business Premium tenants were put on an earlier timeline, so smaller offices may already see users on new Outlook. And "opt-out" means users can still go back during that phase, which is the window to find and fix signature problems before the switch becomes permanent.

What breaks in your signature setup

1. Scripts and Group Policy that write signature files

Most homegrown setups follow the same pattern. A PowerShell script or a Group Policy preference reads each user's details from Active Directory or Entra ID, writes an .htm signature file into %APPDATA%\Microsoft\Signatures, and sets a registry key so classic Outlook uses it by default.

New Outlook does not read that folder. Its signatures live in the cloud, alongside the mailbox, and they sync between new Outlook and Outlook on the web. A Microsoft Q&A answer from December 2024 also says these cloud signatures cannot be reached through Microsoft Graph. When Microsoft added an admin setting to pause cloud signatures in 2023, it said it planned to give admins an API to set signatures for users, but it gave no date. So a script that worked for years can leave users on new Outlook with no signature, or with whatever they typed in themselves.

2. COM add-ins

Microsoft is clear on this one. COM and VSTO add-ins are not supported in new Outlook for Windows. They keep working in classic Outlook only. If your signature tool installs a COM add-in on each PC, it stops inserting signatures the day a user is switched.

3. Tools that depend on EWS

Some older signature tools and scripts use Exchange Web Services to reach mailboxes. Microsoft began blocking EWS in Exchange Online tenants that took no action on 1 October 2026, and it plans to shut EWS down completely on 1 April 2027. This is a separate deadline from new Outlook, but it lands in the same months. If a vendor or an internal script uses EWS, it needs a replacement before April.

4. Two signatures on one email

During the move, some users will have a personal signature saved in Outlook as well as the company one. The result is an email with two signatures, or the wrong one. Microsoft lets admins pause cloud signatures in Outlook on the web and new Outlook with one Exchange Online PowerShell setting:

Set-OrganizationConfig -PostponeRoamingSignaturesUntilLater $true

Classic Outlook still needs a registry setting for the same result. Decide which way you want this before the pilot, so users are not confused twice.

What keeps working

Web add-ins are the part of the Outlook platform Microsoft is building on. They run in new Outlook with no extra work from the vendor, and they also run in classic Outlook, Outlook on the web and Outlook for Mac.

The feature that matters for signatures is called event-based activation. It lets a web add-in start by itself when a user opens a new email and insert the signature, so nobody has to click anything. Microsoft supports it in new and classic Outlook on Windows, on the web and in the new Mac interface. Classic Outlook needs at least Windows 10 version 1903 for it. Outlook for iOS and Android support it for new emails from version 4.2352.0, with a Microsoft 365 subscription.

That makes a web add-in with event-based activation the one method that covers classic Outlook today and new Outlook after March, on the same deployment.

A checklist for the months before March 2027

Find out how signatures get into email today. Look for logon scripts, Group Policy preferences, Intune scripts that write files, COM add-ins and any third-party tool. Many companies run more than one of these without knowing it.
List your COM add-ins. Microsoft's own migration advice starts here: identify the COM add-ins people actually use and find a web add-in to replace each one.
Ask every vendor and script owner whether they use EWS. Then check your tenant's EWSEnabled setting in Exchange Online PowerShell, because a blocked EWS app fails quietly.
Move signatures to a web add-in deployed from the Microsoft 365 admin center. A Global admin or an Exchange admin deploys it under Settings, then Integrated apps, to everyone or to chosen users and groups. Microsoft's limits apply: it can take up to 24 hours to reach every user, users in nested groups do not get it, and security groups that are not mail-enabled are not supported.
Decide what happens to personal signatures. Pause cloud signatures with the setting above, or tell users to delete their own signature on a set date.
Run a pilot now. Pick ten people, switch them to new Outlook, and check a new email, a reply, a forward and a message sent from a phone. Fix what you find while everyone else is still on classic Outlook.
Clean your directory data. A central signature is only as good as the job titles, phone numbers and office addresses in Entra ID. A pilot is the cheapest moment to find the gaps.
Put a recheck in your calendar. Read MC949965 again in January and in February 2027, because the start date has already moved once.

Intune and new Outlook

Intune shows up in almost every question admins ask about this move, so it helps to be exact about its role. Intune manages devices, apps and policies, and many companies use it to keep Outlook up to date on every laptop.

Intune is not how an Outlook web add-in reaches users. Microsoft deploys Office add-ins to users and groups from the Microsoft 365 admin center, and deploying an add-in means preinstalling it for those users. An Intune-managed laptop gets the add-in when the user signs in to Outlook with an account it was assigned to. So you do not need to package anything in Intune. You do need the Outlook builds on those devices to be recent enough for event-based activation.

How SyncSignature handles new Outlook

SyncSignature uses an Outlook web add-in, listed on Microsoft AppSource. Here is what that means for this move, as of November 2026.

It works in new and classic Outlook. The add-in starts by itself when a user begins a new email and inserts their signature. It also works in Outlook on the web and on mobile.
You deploy it once. An admin deploys it from the Microsoft 365 admin center to the whole company or to chosen groups. Users do not install anything.
It reads your directory, read-only. SyncSignature reads Entra ID through Microsoft Graph with read-only permissions (User.Read.All, Group.Read.All, Directory.Read.All) and never writes to your directory.
It does not use EWS. Microsoft's EWS shutdown does not affect it.
It does not route or read your email. SyncSignature does not route or read email, stores data on AWS in Mumbai, and provides a DPA on request.
It signs calendar invites too. When a user creates a calendar event in Outlook, the add-in adds their signature to the invite. Outlook cannot do this on its own yet: Microsoft's roadmap entry for inserting signatures into calendar events (ID 422817) was still marked in development when we checked on 4 November 2026.
Directory changes come through on a schedule. Directory sync runs every 24 hours, or on demand with one click.
Setup is short. Expect about 2 hours for a 50-seat team, or 10 to 20 minutes when your directory data is already complete.

Yanolja runs 800+ signatures on SyncSignature.

There are limits, and it is better to know them before a pilot than after. Shared mailboxes are not supported. On Microsoft 365, the same signature can be turned on or off for replies and forwards, but a separate, different reply signature is not possible. Apple Mail and other clients outside Outlook use copy and paste. And Microsoft's own version requirements for event-based activation apply to every add-in, ours included.

You can start a 7-day trial with no card and run your new Outlook pilot on it, or see pricing. The setup steps are in our guide to installing email signatures in Microsoft 365, and troubleshooting Microsoft 365 signature installation covers the common problems. For the bigger picture, see Microsoft 365 signature management, directory sync and enterprise email signature management.

Frequently asked questions

What is the modern way to manage email signatures now that scripts don't work in new Outlook?

Use an Outlook web add-in that inserts the signature with event-based activation, deployed from the Microsoft 365 admin center. New Outlook does not read the local Signatures folder that scripts write to, and it does not run COM add-ins. A web add-in works in both classic and new Outlook, on the web and on mobile, from one deployment.

When will Microsoft move enterprise users to new Outlook?

As of 4 November 2026, Microsoft plans to start the opt-out phase for Microsoft 365 Enterprise users in March 2027. Users can switch back during that phase. Microsoft says it will give 12 months' notice before the cutover phase, after which users can no longer return to classic Outlook. Check Message Center post MC949965 for changes.

Is there email signature software that works with new Outlook and Intune?

Yes. Any signature tool built as an Outlook web add-in works in new Outlook, and it reaches Intune-managed devices through the user's Microsoft 365 account, since add-ins are deployed to users from the Microsoft 365 admin center. SyncSignature works this way. Check that the Outlook builds on your managed devices support event-based activation.

What should an email signature tool support to work with Intune and new Outlook?

Look for four things. It should be a web add-in, not a COM add-in. It should insert signatures with event-based activation, so users do not have to click. It should deploy from Integrated apps in the Microsoft 365 admin center. And it should not depend on EWS, which Microsoft shuts down in Exchange Online in April 2027.

Are there cloud-based signature tools built for Microsoft 365 and new Outlook?

Yes. Cloud signature tools that use an Outlook web add-in and read user details from Entra ID through Microsoft Graph are built for this setup. SyncSignature reads Entra ID with read-only permissions, deploys through the Microsoft 365 admin center, and inserts signatures in new and classic Outlook, on the web and on mobile.

Does the EWS retirement affect email signature tools?

It affects any tool or script that uses Exchange Web Services. Microsoft began blocking EWS in Exchange Online tenants without an allow list on 1 October 2026 and plans a full shutdown on 1 April 2027. Ask your vendor directly. SyncSignature does not use EWS.

Can an email signature appear in Outlook calendar invites?

Not with Outlook's own signature settings. As of 4 November 2026, Microsoft's roadmap lists inserting signatures into calendar events (ID 422817) as in development. A signature add-in can do it today: SyncSignature's Outlook add-in adds the user's signature when they create a calendar event, as well as when they start a new email.

Can users still switch back to classic Outlook?

Yes, during the opt-out phase that starts in March 2027. Once Microsoft completes the later cutover phase, they cannot. Use the time before cutover to move signatures to a method that works in both versions.

Sources

Checked 4 November 2026.

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New Outlook in March 2027: What Breaks in Your Email Signatures and How to Fix It Now